It is well known in the art to utilize embossing to decorate and thicken tissue products. A few examples of using embossing in this manner are disclosed, for example, in U.S. Pat. No. 2,043,351 to Fourness, U.S. Pat. No. 4,189,344 to Busker, and U.S. Pat. No. 5,356,364 to Veith. Using embossing to increase sheet caliper (thicken), has allowed bathroom tissue producers to reduce the number of sheets within the roll while retaining the same package size (roll diameter). This has been a common practice in the bathroom tissue market for many years, particularly for household tissue products sold at grocery stores.
One means of imparting bathroom tissue with a decorative embossment, referenced in U.S. Pat. No. 4,659,608 to Schultz, is commonly referred to as “spot embossing.” Spot embossing generally involves discrete embossing elements that are about ½ inch by ½ inch to about 1 inch by 1 inch in size (about 0.25 to about 1 square inch in surface area). These discrete spot embossing elements are spaced about ½ inch to about 1 inch apart. They are typically engraved in a steel roll about 0.060 inch in relief. In most cases spot embossing is carried out with a steel engraved roll (male elements) and a rubber covered backing roll. The design of spot embossing patterns covers a wide range of decorative shapes such as, for example, flowers, butterflies, geometric shapes and patterns, logos and trademarks. Spot embossing is commonly used not only to decorate, but also to increase sheet caliper.
While the prior art embossing methods are useful for decorating and thickening tissue products, they may be limited in their ability to affect other important product properties, such as tensile strength. This is particularly true when attempting to balance both decorating the tissue and modulating its strength. Therefore there is a need for a method of embossing soft, thick tissue sheets which provides a lasting embossing pattern in tissue sheets, but which also degrades the sheets tensile in a controlled and predictable fashion.